U.S. patent number 4,787,981 [Application Number 06/928,585] was granted by the patent office on 1988-11-29 for process for purification of crude glyceride oil compositions.
This patent grant is currently assigned to Nitto Electric Industrial Co., Ltd., Pinoru Oil Mills Co.. Invention is credited to Yutaka Isooka, Akio Iwama, Masaaki Kasai, Yoshitaka Kazuse, Kaoru Nagano, Seiichi Tanahashi, Kentaro Tasaka, Fujihiko Tsubone.
United States Patent |
4,787,981 |
Tanahashi , et al. |
November 29, 1988 |
**Please see images for:
( Certificate of Correction ) ** |
Process for purification of crude glyceride oil compositions
Abstract
A process for purification of crude glyceride oil compositions
which comprises diluting a crude glyceride oil composition
containing gum material and wax as main components of impurities
with an organic solvent, bringing the diluted crude glyceride oil
composition into contact with a semipermeable membrane composed of
polyimide consisting essentially of a repeating unit represented by
the general formula: ##STR1## wherein R.sup.1 represents a divalent
organic group, under pressure to obtain a semipermeable membrane
permeable liquid in which the gum material in the glyceride oil
after removal of said organic solvent is 100 ppm or less, carrying
out bleaching of the glyceride oil obtained from said semipermeable
membrane permeable liquid with at least one kind of an adsorbent
selected from the group consisting of clay, activated clay,
activated carbon and bone black, and then carrying out deodorizing
to obtain a purified glyceride oil.
Inventors: |
Tanahashi; Seiichi (Aichi,
JP), Nagano; Kaoru (Aichi, JP), Kasai;
Masaaki (Aichi, JP), Tsubone; Fujihiko (Aichi,
JP), Iwama; Akio (Osaka, JP), Kazuse;
Yoshitaka (Osaka, JP), Tasaka; Kentaro (Osaka,
JP), Isooka; Yutaka (Osaka, JP) |
Assignee: |
Pinoru Oil Mills Co. (Tokyo,
JP)
Nitto Electric Industrial Co., Ltd. (Osaka,
JP)
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Family
ID: |
13642531 |
Appl.
No.: |
06/928,585 |
Filed: |
November 10, 1986 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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695134 |
Jan 25, 1985 |
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493190 |
May 10, 1983 |
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Foreign Application Priority Data
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May 10, 1982 [JP] |
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58-77748 |
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Current U.S.
Class: |
210/639; 210/651;
210/669; 426/417; 554/191; 554/83 |
Current CPC
Class: |
C11B
3/001 (20130101) |
Current International
Class: |
C11B
3/00 (20060101); B01D 013/00 () |
Field of
Search: |
;210/638,639,649,650,651,654,669,806 ;260/403,428,428.5,424
;426/417,490,662 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2651761 |
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May 1977 |
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DE |
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3138498Al |
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Jun 1982 |
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DE |
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50-153010 |
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May 1975 |
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JP |
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52-84206 |
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Jul 1977 |
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JP |
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55-152507 |
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Nov 1980 |
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JP |
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2051664A |
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Jan 1981 |
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GB |
|
2084606 |
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Apr 1982 |
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GB |
|
Other References
Porter, M. C. et al., "Membrane Ultrafiltration", Chem. Tech., Jan.
1971, pp. 56-63. .
Chemical Abstract, vol. 91, No. 7, Aug. 1979, p. 545, No.
54948n..
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Primary Examiner: Hruskoci; Peter
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak &
Seas
Parent Case Text
This is a continuation of application Ser. No. 695,134, filed
1/25/85, now abandoned, which is a continuation of application Ser.
No. 493,190, filed 5/10/83, now abandoned.
Claims
What is claimed is:
1. A process for purification of crude glyceride oil compositions
comprising:
(A) diluting a crude glyceride oil composition containing gum
material and wax as main components of impurities, with an organic
solvent,
(B) bringing the diluted crude glyceride oil composition into
contact with a semipermeable membrane having a molecular weight
cut-off value of 10,000-20,000, comprising polyimide consisting
essentially of a repeating unit represented by the general formula:
##STR5## wherein R.sup.1 represents a divalent organic group, under
pressure to obtain a semipermeable membrane permeable liquid in
which the gum material in the glyceride oil after removal of said
organic solvent is 100 ppm or less, and subjecting the
semipermeable membrane permeable liquid to acid treatment by adding
at least one kind of acid or salt thereof selected from the group
consisting of oxalic acid, citric acid, acetic acid, glacial acetic
acid, phosphoric acid, sodium phosphate, sodium polyphosphate and
sulfuric acid, wherein the amount of the acid added is 0.001 to
0.5% by weight based on the weight of the glyceride oil,
(C) carrying out bleaching of the glyceride oil obtained from said
semipermeable membrane permeable liquid with at least one kind of
an adsorbent selected from the group consisting of clay, activated
clay, activated carbon and bone black, wherein the adsorption
treatment is carried out by dispersing the adsorbant in the
degummed oil and heating to a temperature of 80.degree. to
120.degree. C. for five to sixty minutes with stirring under a
reduced pressure of 1 to 200 mm Hg abs, and then
(D) carrying out deodorizing to obtain a purified glyceride oil
wherein the deodorizing is carried out by stripping the glyceride
oil with sparge steam in an amount of 2 to 20% by weight based on
the weight of the glyceride oil at a temperature of 240.degree. to
270.degree. C. under a reduced pressure of 1 to 10 mm Hg abs,
wherein the cut-off value is a minimum molecular weight of a
polyethylene glycol having a removal rate of at least 95%, as
measured using toluene solutions of polyethylene-glycols having
different average molecular weights at a temperature of 25.degree.
C. and a pressure of 3 kg/cm.sup.2.
2. The process as claimed in claim 1, wherein the organic solvent
is selected from the group consisting of hydrocarbons, lower free
fatty acid esters, aliphatic ketones, and mixtures thereof and has
a molecular weight of 50 to 200.
3. The process as claimed in claim 1, wherein the organic solvent
is hexane.
4. The process as claimed in claim 1, wherein contacting the
semipermeable membrane is conducted at a temperature of 0.degree.
to 100.degree. C.
5. The process as claimed in claim 1, wherein the crude glyceride
oil composition is diluted with the organic solvent to adjust the
glycerider oil content to 10 to 90% by weight.
6. The process as claimed in claim 1, wherein the amount of the
adsorbent used is 0.01 to 5% by weight based on the weight of the
glyceride oil.
7. The process as claimed in claim 1, wherein R.sup.1 is
represented by the general formula: ##STR6## wherein X represents a
divalent linking group.
8. The process as claimed in claim 7, wherein X is --CH.sub.2 -- or
--O--.
9. The process as claimed in claim 1, wherein the semipermeable
membrane is prepared by dissolving the polyimide and a swelling
agent in an organic solvent compatible with a coagulation solvent
to prepare a dope, applying the dope to a support, dipping the dope
applied support in a coagulation solvent which does not dissolve
the polyimide but dissolves the swelling agent and is compatible
with the organic solvent and coagulating the polyimide.
10. The process as claimed in claim 9, wherein the swelling agent
is selected from the group consisting of ethylene glycol,
diethylene glycol and triethylene glycol.
11. The process as claimed in claim 1, wherein said polyimide has
an imidation rate defined as: ##EQU2## of about 70% or more.
12. The process as claimed in claim 1, wherein said diluted crude
glyceride oil composition is brought into contact with said
semipermeable membrane under a pressure of 0.1 to 50 kg/cm.sup.2,
gauge pressure.
13. The process as claimed in claim 1, wherein said semipermeable
membrane has a molecular weight cut-off value of 20,000.
Description
FIELD OF THE INVENTION
The present invention relates to a process for purification of
crude glyceride oil compositions.
BACKGROUND OF THE INVENTION
Vegetable oils usually used as food oils include soybean oil,
rapeseed oil, cotton seed oil, safflower oil, corn germ oil,
sunflower oil, rice bran oil and the like. In producing such
vegetable oils, depending on the amount of oil contained therein, a
raw material is pressed or the raw material is extracted with an
organic solvent such as hexane to obtain miscella, and then the
organic solvent is removed by evaporation from the miscella to
yield a crude glyceride oil composition. Such a crude glyceride oil
composition generally contains 0.5 to 10% by weight of impurities
including phospholipid such as lecithin, etc., as main ingredient,
waxes such as higher alcohols, etc., organic sulfur compounds,
peptides, free fatty acids, hydrocarbons, carbohydrates, lower
aldehydes, lower ketones, sterols, dye compounds and a small amount
of metals, etc. These impurities are not desirable on quality of
the products, because they cause polymerization or decomposition
during preservation or on using or heating to result in oil
coloration, generation of unpleasant odors and acceleration of
oxidation or deterioration. It is necessary, therefore, to remove
the gum materials, waxes and other impurities from the crude oil as
much as possible.
Hitherto, in the oil industry, water is added to the crude oil to
hydrate the gum material composed mainly of phospholipid, followed
by swelling and coagulating the same to degum by centrifugal
separation. Since the resulting degummed oil still contains about
0.2 to 1.0% by weight of gum material, it is usually subjected to
chemical refining using chemicals such as alkali or acid, etc., to
carry out removal of gum material and acid, namely, removal of
mainly residual phospholipids and free fatty acids, followed by
heating in vacuum together with an adsorbent such as activated
clay, etc., to remove colors and other impurities such as heavy
metals, free fatty acids, soaps or gum materials, etc., which
cannot be removed by the above-described chemical refining.
Further, it is generally processed in a dewaxing step for removing
waxes and saturated tri- or diglycerides, etc., which crystallize
or cause turbidity in the oil at a low temperature. Thereafter,
unpleasant odor components such as lower aldehydes, ketones and
free fatty acids, etc., are removed in the final step to obtain a
purified glyceride oil having a gum content of 50 ppm or less as
the final product.
However, the above-described prior purification process requires
complicated chemical treatments involving chemical reactions except
for the deodorizing step as the final purification step, and
further it is desirable to obtain a purified glyceride oil suitable
for food that the phospholipid content in the glyceride oil after
the treatment for removing acids with alkalis is 100 ppm or less in
the bleaching and deodorizing steps. Thus, in the prior art
process, it is necessary to carry out repeatedly the gum removal
operation. Consequently, not only a large amount of chemicals is
required and a considerable amount of glyceride oil is lost, but at
least a part of the glyceride oil deteriorates by various chemical
treatments for removing gum material and acid to have a harmful
influence upon the product glyceride oil and various secondary
products obtained therefrom. Further, in order to carry out
treatment for drainage which is remarkably polluted as the result
of various chemical treatments or treatment for foots formed in the
deacidification step, chemicals, equipment and expense are
additionally required.
In order to remove such disadvantages, a novel process for
purification of crude glyceride oil compositions was proposed in
Japanese Patent Application (OPI) No. 153010/75 (the term "OPI" as
used herein refers to a "published unexamined Japanese patent
application"). In accordance with this process, after a crude
glyceride oil composition is diluted with an organic solvent such
as hexane, etc., it is brought into contact with an ultrafiltration
membrane made of polysulfone, polyacrylonitrile or polyamide under
pressure and the organic solvent is removed from a membrane
permeable solution to obtain a degummed oil. However, according to
this process, a removal rate to phospholipids in the crude
glyceride oil composition is not sufficiently high because of
characteristics of the ultrafiltration membrane, and, in the case
of a crude glyceride oil composition containing several % by weight
of gum material, it is difficult to reduce a gum material content
in the degummed oil to 100 ppm or less which is the amount capable
of effectively purifying so as to use for food by the
above-described bleaching and deodorizing steps by one step
membrane treatment described above. Thus, as described in Japanese
Patent Application (OPI) No. 84206/77, an adsorption treatment
using an expensive adsorbent such as alumina or silica is
additionally required before or after the membrane treatment for
miscella. As the result, technical and commercial advantages of the
membrane treatment which is substituted for purification by
chemical treatment are remarkably reduced. By the way, in case that
the crude glyceride oil composition contains 2% by weight of gum
material, the removal rate of the membrane for gum material should
be 99.5% or more in order to reduce the gum material content in the
resulting degummed oil to 100 ppm or less.
Further, in any of the above-described processes, since the
ultrafiltration membrane used does not have sufficiently high
resistance to glyceride oils and organic solvents for dilution and
it easily softens at an elevated temperature, the molecular weight
cut-off varies and removal ability for gum material is lost.
Therefore, it is desirable that the membrane treatment is generally
carried out at a comparatively low temperature of 10.degree. to
20.degree. C. As the result, since miscella having a comparatively
high viscosity is subjected to membrane treatment, the amount of
the permeable liquid is small and the treatment requires a long
period of time. It is not preferred to reduce the glyceride
concentration in the miscella, because the amount to be treated
becomes large, though the viscosity reduces to increase the amount
of the permeable liquid.
SUMMARY OF THE INVENTION
As a result of earnest studies to overcome the above-described
various problems in purification of crude glyceride oil
compositions by the membrane treatment, it has been found that a
degummed oil having a gum material concentration of 100 ppm or less
can be obtained by the process which comprises diluting a crude
glyceride oil composition containing glyceride oil and phospholipid
and wax as main impurities with, preferably, an organic solvent,
carrying out membrane treatment using a semipermeable membrane of
polyimide having a specified structural unit to obtain a permeable
liquid in a large amount, from which the phospholipid is removed at
a removal rate of 99.5% or more, and removing the organic solvent
from the permeable liquid, and, consequently, purified glyceride
oil having a high quality which is suitable for food oil can be
obtained by carrying out bleaching of the resulted degummed oil
with an inexpensive adsorbent such as clay or activated clay, etc.,
and thereafter carrying out deodorizing. Thus, the present
invention has been made.
Accordingly, an object of the present invention is to provide a
process for obtaining a purified glyceride oil comprising diluting
a crude glyceride oil composition containing gum material and wax
as main components of impurities with an organic solvent, bringing
the diluted crude glyceride oil composition under pressure into
contact with a semipermeable membrane composed of polyimide
consisting essentially of a repeating unit represented by the
general formula: ##STR2## wherein R.sup.1 represents a divalent
organic group, to obtain a semipermeable membrane permeable liquid
in which the gum material in the glyceride oil after removal of the
organic solvent is 100 ppm or less, carrying out bleaching of the
glyceride oil obtained from the semipermeable membrane permeable
liquid with at least one kind of adsorbent selected from clay,
activated clay, activated carbon and bone black, and carrying out
deodorizing to obtain a purified glyceride oil.
DETAILED DESCRIPTION OF THE INVENTION
The semipermeable membranes composed of the above-described
polyimide suitably used in the present invention have been
described in U.S. Pat. No. 4,240,914. In the present invention, a
semipermeable membrane comprising a polyimide represented by the
above-described general formula wherein R.sup.1 is represented by
the general formula: ##STR3## wherein X represents a divelent
linking group, is preferably used.
Examples of X include --CH.sub.2 --, --C(CH.sub.3).sub.2 --, --O--,
--SO.sub.2 --, etc. In particular, polyimides wherein X is
--CH.sub.2 -- or --O--, which have a constant molecular weight
cut-off over a long period of time even when bringing into contact
with crude glyceride oil compositions heated to high temperatures,
are preferred.
The present invention can used polyimides consisting essentially of
the above-described repeating unit which have an imidation rate
defined as ##EQU1## of about 70% or more, preferably 90% or more,
and most preferably 98 to 100%. Further, the inherent viscosity of
the polyimides (measured at 30.degree. C. in N-methyl-2-pyrrolidone
solution) is 0.55 to 1.00, preferably 0.6 to 0.85, and a number
average molecular weight thereof is 20,000 to 120,000, preferably
30,000 to 80,000.
The process for producing semipermeable membranes having an
anisotropic structure such as an ultrafiltration membrane or a
reverse osmosis membrane, etc., consisting of the above-described
general formula has been disclosed in Japanese Patent Application
(OPI) Nos. 71785/79 and 94477/79. However, in the process of the
present invention, it is preferred to use a semipermeable membrane
produced by the process which comprises dissolving the above
described polyimide and a swelling agent represented by the general
formula:
wherein R.sup.2, R.sup.3 and R.sup.4 each represents a hydrogen, a
methyl group or an ethyl group, and n represents an integer of 1 to
5 where R.sup.2 is a hydrogen and an integer of 1 to 3 where
R.sup.2 is a methyl group or an ethyl group, in an organic solvent
(hereinafter referred to as dope solvent) compatible with a
coagulation solvent such as water, etc., to prepare a dope,
applying the resulting dope to a suitable support, dipping it in a
coagulation solvent which does not dissolve the above-described
polyimide but dissolves the swelling agent and is compatible with
the above-described dope solvent, and coagulating the
above-described polyimide to form a membrane, as described in
Japanese Patent Application (OPI) No. 152507/80.
In the above-described swelling agent, n is preferably an integer
of 2 or 3 where R.sup.2 is a hydrogen, and n is preferably an
integer of 1 or 2 where R.sup.2 is a methyl group or an ethyl
group. Accordingly, examples of the swelling agent include
(poly)ethylene glycols and methyl or ethyl derivatives thereof such
as ethylene glycol, diethylene glycol, triethylene glycol, ethylene
glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene
glycol dimethyl ether, diethylene glycol monomethyl ether,
diethylene glycol dimethyl ether, triethylene glycol monomethyl
ether, etc. Further, examples of the dope solvent include
N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone,
N-methyl-2-piperidone, dimethylformamide, dimethylacetamide,
dimethyl sulfoxide, tetramethyl urea, sulforan, etc.
Further, as the coagulation solvent, water is generally used, but
solvents which are compatible with the dope solvent and dissolve
the swelling agent but coagulate the above-described polyimide may
be used. For example, mixed solvents of at least one of methanol,
ethanol, acetone, ethylene glycol, diethylene glycol and diethylene
glycol monomethyl ether and water can be used. Of course, these can
be used alone as the coagulation solvent.
Since the process for producing semipermeable membranes from a dope
containing the polyimide and the swelling agent has been described
in the above-described Japanese OPI references, the details thereof
are omitted. It is preferred that the amount of the polyethylene
glycol or ether derivatives thereof represented by the
above-described general formula used is 30 to 300 parts by weight,
preferably 50 to 200 parts by weight, based on 100 parts by weight
of the polyimide, and the concentration of the polyimide in the
dope is 5 to 30 parts by weight.
The semipermeable membranes composed of the polyimide used in the
present invention usually have a molecular weight cut-off of 10,000
to 100,000, preferably 10,000 to 30,000, and semipermeable
membranes called ultrafiltration membranes are generally preferred
to use. When the molecular weight cut-off value is too small, the
amount of the permeable liquid tends to be decreased. On the other
hand, when this value is too high, the gum material separating
ability tends to be poor.
The molecular weight cut-off can be determined by measuring the
removal rate of the semipermeable membrane to a solute having a
known molecular weight. Practically, it is preferred to measure the
removal rate of the semipermeable membrane using a toluene solution
of polyethylene glycol having a known average molecular weight and
a monodisperse molecular weight distribution as a solute
(concentration: 5,000 ppm). In the invention, therefore, the
removal rate of the membrane is measured using toluene solutions of
polyethylene glycols having different average molecular weights at
a temperature of 25.degree. C. and a pressure of 3 kg/cm.sup.2, and
the minimum molecular weight of the polyethylene glycol having a
removal rate of at least 95% is determined to be the molecular
weight cut-off of the membrane.
Lecithin which is a typical component of phospholipids has a
molecular weight nearly equal to that of triglyceride. At the
membrane treatment conditions of the present invention, however,
several ten to several hundred lecithin molecules associate
together to form miscelle. Therefore, by bringing into contact with
a semipermeable membrane having a molecular weight cut-off in the
above-described range, phospholipid is almost completely removed by
the membrane, whereby a degummed oil having a phospholipid
concentration of 100 ppm or less can be obtained.
In the present invention, organic solvents, preferably, are used in
order to accelerate miscelle formation of phospholipid while at the
same time diluting the crude glyceride oil composition. Such
organic solvents are required to have a property of not dissolving
the above-described polyimide semipermeable membrane. The molecular
weight thereof is preferably smaller than that of the glyceride oil
and is usually 50 to 200, preferably 60 to 150. Examples of the
organic solvents include aliphatic hydrocarbons such as pentane,
hexane, heptane, octane, etc., alicyclic hydrocarbons such as
cyclopropane, cyclopentane, cyclohexane, cycloheptane, etc.,
aromatic hydrocarbons such as benzene, toluene, xylene, etc.,
aliphatic ketones such as acetone, methyl ethyl ketone, etc., and
lower fatty acid esters such as ethyl acetate, butyl acetate, etc.,
which can be used alone or as a mixture of two or more of them.
Aliphatic hydrocarbons such as hexane are preferably used.
The miscella prepared by diluting the crude glyceride oil
composition with the organic solvent usually contains 10 to 90% by
weight, preferably 20 to 50% by weight of glyceride oil, but it is
not limited thereto. Further, the crude glyceride oil composition
can be directly subjected to the membrane treatment without
diluting with the organic solvent.
Depending on the type of oil seed, the crude glyceride oil
composition can be extracted directly from the oil seed with the
organic solvent. In the present invention, the thus-extracted
liquid may be subjected to the membrane treatment as such. The term
"extraction" is construed to be the same as the dilution with the
organic solvent. In addition, glyceride oil compositions obtained
by distilling away the solvent after the solvent extraction by the
prior purification process can be used as the crude glyceride oil
compositions in the present invention, and, of course, compositions
obtained by pressing an oil seed can be used as the crude glyceride
oil. Furthermore, if desired, gum material-containing glyceride oil
obtained at any desired stage of the prior purification process can
be used as the crude glyceride oil. The term "miscella" is used
hereinafter to refer to a solution of the crude glyceride oil
composition in the organic solvent, as described above.
In the present invention, the miscella of the crude glyceride oil
composition, namely, the solution of the crude glyceride oil
composition in the organic solvent is then brought into contact
with the polyimide semipermeable membrane under pressure at a
temperature at which evaporation of the organic solvent is not
significant, which is usually from 0.degree. C. to 150.degree. C.,
preferably from 0.degree. C. to 100.degree. C. and most preferably
0.degree. C. to 80.degree. C. Generally, by raising the treatment
temperature, the amount of the permeable liquid processed can be
increased. In the present invention, even if the membrane treatment
is carried out at a higher temperature, the polyimide semipermeable
membrane maintains its molecular weight cut-off at a substantially
constant level, and thus the membrane permeable liquid contains
substantially no phospholipid.
At a temperature lower than 0.degree. C., however, the amount of
the permeable liquid is too small from a practical viewpoint. On
the other hand, the treatment temperature is too high, there is the
danger that the miscelle composed mainly of phospholipid is
thermally decomposed and cannot be effectively removed by the
membrane.
Further, in carrying out membrane treatment, the miscella of the
crude glyceride oil composition is brought into contact with a
semipermeable membrane under a pressure of 0.1 to 50 kg/cm.sup.2
(gauge pressure; hereinafter, all are the same) depending on the
shape of the semipermeable membrane used. For example, in case of
using a capillary semipermeable membrane having an inner diameter
of about 0.1 to 2 mm, it is pressured at a pressure of 0.1 to 8
kg/cm.sup.2, preferably 0.3 to 5 kg/cm.sup.2, and in case of using
a tubular semipermeable membrane wherein a semipermeable membrane
is formed on the inside of the porous support tube having an inner
diameter of about 2 to 50 mm, it is pressurized at a pressure of 2
to 50 kg/cm.sup.2, preferably 5 to 20 kg/cm.sup.2. Generally, when
the pressure is too low, the permeation rate of the glyceride oil
is low, though it depends upon the shape of the membrane. On the
other hand, when the pressure is too high, the membrane is easily
compacted or damaged.
Further, in the present invention, it is preferred that the
miscella of the crude glyceride oil composition is brought into
contact under pressure with the semipermeable membrane under the
above-described conditions with continuously circulating it till at
least 50%, preferably 66 to 98%, of the purified glyceride oil
based on the crude glyceride oil composition is recovered as a
membrane permeable liquid. If necessary, the organic solvent is
added to the miscella to supplement the permeated one. Concerning
the flow rate of the miscella of the crude glyceride oil
composition to the membrane face, it is preferred that the linear
velocity to the membrane face is 0.1 to 8 m/second, preferably 0.5
to 3 m/second. For example, in the process of the present
invention, the miscella of the crude glyceride oil composition is
continuously circulated through a tubular semipermeable membrane by
means of a pump, etc. In this case, when the linear velocity
parallel to the membrane face of the miscella of the crude
glyceride oil composition is too low, the concentration
polarization of impermeable components such as phospholipid, etc.,
on the membrane face becomes great, by which permeation of the
glyceride oil is prevented, and when it is too large, energy
efficiency of the pump deteriorates.
The process of the present invention is suitable for the refining
of crude vegetable glyceride oil compositions containing a large
amount of phospholipid such as lecithin, and, in addition, it can
be applied to the refining of crude animal glyceride oil
compositions. Further, since lecithin, etc., are useful and
valuable materials, they can be recovered, if necessary, from the
membrane impermeable liquid. Usually, after the membrane
impermeable liquid is diluted again with the organic solvent such
as hexane, etc., and subjected to membrane treatment according to
the present invention, the organic solvent is removed from the
membrane impermeable liquid, by which phospholipid having a high
purity can be obtained.
From the ultrafiltration treated miscella as described above, the
organic solvent is then removed by distillation or other means. The
removal of the solvent from such degummed miscella is carried out
by the same method as that of the prior art. The degummed oil
subjected to the membrane treatment by the process of the present
invention has a residual gum material content of 100 ppm or less
and, in preferable case, 50 ppm or less. At the same time, waxes in
the composition are substantially removed, when the membrane
treatment temperature of the crude glyceride oil composition is in
a range of 0.degree. to 80.degree. C. Such dewaxing of the crude
glyceride oil composition by the membrane treatment according to
the present invention can be effectively carried out not only for
cotton seed oil, safflower oil, corn germ oil, rice bran oil, etc.,
which contain a large amount of waxes but also for soybean oil and
rapeseed, etc., which are difficult to remove waxes by the prior
methods because of containing waxes in a small amount.
Consequently, according to the present invention, since the
degumming and dewaxing can be carried out at the same time by the
membrane treatment of the crude glyceride oil composition at a
temperature range of 0.degree. to 80.degree. C. regardless of the
amount of waxes, the dewaxing step which is the essential step in
the prior purification process can be abridged. Therefore, much
energy required hitherto for the dewaxing step comprising cooling
and filtration of the glyceride oil composition is not required and
the loss of glyceride oil accompanying to dewaxing can be
prevented.
According to the present invention, the degummed and dewaxed
glyceride oil obtained as described above is subjected to bleaching
and deodorizing as described hereinafter, by which a highly
purified glyceride oil suitable for the food oil can be
obtained.
In order to carry out bleaching of the degummed oil in the present
invention, at least one kind of adsorbent selected from
finely-divided clay, activated clay, activated carbon and bone
black, which are used for bleaching of the conventional chemically
refined oil, can be used. The adsorption treatment is carried out
by dispersing the adsorbent in the degummed oil and heating to a
temperature of 80.degree. to 120.degree. C. for 5 to 60 minutes
with stirring under a reduced pressure of 1 to 200 mm Hg abs. The
amount of the above-described adsorbent used in the present
invention is in a range of 0.01 to 5% by weight, preferably 0.1 to
2% by weight, based on the weight of the degummed oil.
Of course, the bleaching of the degummed oil by adsorption can be
carried out by passing the degummed oil through a column packed
with the adsorbent. Further, in this adsorption treatment, not only
colors but also impurities remaining in a small amount in the
degummed oil can be removed.
Furthermore, in order to improve the quality of the purified oil,
in the present invention, acid treatment can be carried out before
the adsorption treatment by adding organic acids, inorganic acids
or metal salts thereof which are permitted to use as food
additives. Examples of organic acids include citric acid, oxalic
acid, acetic acid, glacial acetic acid, etc., and examples of
inorganic acids include phosphoric acid, sodium phosphate, sodium
polyphosphate, sulfuric acid, etc. A suitable amount thereof is
0.001 to 0.5% by weight, preferably 0.005 to 0.05% by weight, based
on the weight of the degummed oil.
From the glyceride oil after the adsorption treatment, the
adsorbents are separated and removed by usually a pressure
filtration method. The above-described acids added, if necessary,
to the degummed oil are simultaneously removed in this step by
adsorbing onto the adsorbent.
The bleaching oil is then subjected to deodorizing. The deodorizing
is usually carried out by stripping the glyceride oil with sparge
steam in an amount of 2 to 20% by weight based on the weight of the
glyceride oil at a temperature of 240.degree. to 270.degree. C.
under a reduced pressure of 1 to 10 mm Hg abs. This deodorizing may
be the same as that applied to the conventional chemically treated
degummed oils.
According to the process of the present invention, when the crude
glyceride oil composition containing several % of phospholipids and
waxes is diluted with the organic solvent and subjected to only the
one-step membrane treatment with the semipermeable membrane
composed of polyimide, as described above, it is possible to obtain
a degummed oil containing 100 ppm or less of phospholipids and
waxes by removing the organic solvent. Accordingly, when it is
bleached with an inexpensive adsorbent such as clay or activated
clay, etc., and further subjected to the deodorizing, it can be
highly purified and a purified glyceride oil capable of using
directly for food can be obtained. Namely, according to the present
invention, highly purified glyceride oil capable of using for food
can be obtained by only the physical treatment, namely, membrane
treatment, without requiring multistage chemical treatment, and at
the same time, the yield of the purified glyceride oil is
increased. Moreover, foots and drainages containing a large amount
of chemicals are not produced.
Furthermore, according to the membrane treatment using the
polyimide semipermeable membrane of the present invention,
impurities having a comparatively low molecular weight such as
saccharoses and amino acids, etc., are embedded inside of the
miscella of the phospholipid are removed by the membrane, by which
purified glyceride oil having a remarkably high quality can be
obtained.
In the following, the present invention is illustrated by reference
to Reference Example and Examples.
REFERENCE EXAMPLE
Production of Polyimide Ultrafiltration Membrane
To an N-methyl-2-pyrrolidone solution containing 28% by weight of
polyimide having an imidation rate of 99% or more and an inherent
viscosity (.eta.) of 0.73 which had the above-described general
formula wherein R.sup.1 was ##STR4## 100 parts by weight of
diethylene glycol based on 100 parts by weight of polyimide were
added as a swelling agent to prepare a homogeneous dope. This dope
was applied to the inside of a glass tube by cast coating, and the
glass tube is put into water of 5.degree. C. at once and immersed
for 5 hours to obtain a tubular ultrafiltration membrane having an
inner diameter of 12 mm, a thickness of 200 .mu.m and a molecular
weight cut-off of 20,000.
The module equipped with this membrane was attached to the liquid
passage line for the miscella of crude soybean oil composition as
described in the following.
EXAMPLE 1
A 27 wt% hexane miscella of crude soybean oil containing 2.18% by
weight (based on the weight of soybean oil) of phospholipid, as the
crude glyceride oil composition, was subjected to ultrafiltration
treatment by passing through the above-described membrane module in
circulation under conditions of a pressure of 3 kg/cm.sup.2, a
temperature of 40.degree. C. and a flow rate of 14 l/minute. From
the resulting membrane permeable liquid, hexane was distilled away
to obtain an ultrafiltration treated oil.
25 tons of this oil were heated to about 85.degree. C. A 75%
phosphoric acid solution was added to the ultrafiltration treated
oil in an amount of 0.05% by weight based on the weight of the oil
to carry out acid treatment by stirring. Then, this ultrafiltration
treated oil was additionally heated to 110.degree. C., and
activated clay was added in an amount of 0.8% by weight based on
the weight of the treated oil. After stirred for 30 minutes under
110 mm Hg, activated clay was filtered off by a filter press to
obtain a bleaching oil. This bleaching oil was then heated to
260.degree. C., and deodorizing was carried out by stripping with
sparge steam in an amount of 4.5% by weight based on the bleaching
oil under 4 mm Hg abs for 85 minutes to obtain 20 tons of a
purified soybean oil. The resulting purified soybean oil was
preserved for 3 months in an outdoor storage tank, and a
preservation test was carried out.
Properties of the crude soybean oil used for the membrane
treatment, the ultrafiltration treated oil, the bleaching oil and
the purified oil obtained as described above are shown in Table 1.
For comparison, properties of a purified soybean oil which was
obtained by degumming by the conventional chemical process and,
thereafter, carrying out alkali refining, bleaching, dewaxing and
deodorizing are also shown in Table 1.
According to the process of the present invention, an
ultrafiltration treated oil having a phospholipid content of only
25 ppm was firstly obtained by the membrane treatment and,
thereafter, an edible soybean oil which was not different from the
purified soybean oils obtained by the conventional chemical process
could be obtained by carrying out acid treatment, bleaching and
deodorizing of the ultrafiltration treated oil. Moreover, according
to the process of the present invention, as is clear from the
results of cooling test, the dewaxing was effectively carried out
by only the membrane treatment as compared with the conventional
chemical refining process.
Likewise, results of the preservation test of the purified oil
according to the process of the present invention and the purified
oil according to the conventional chemical process are shown in
Tables 2 and 3, respectively.
(Note) Methods of measurement in analysis column in each table are
as follows.
Acid Value: By a standard of the analytical method described in
Journal of Chemistry Society (JOCS) (1971)
Color: Lovibond colorimetry by a standard of the analytical method
(JOCS, 1971). A 1 inch cell is used for crude soybean oil and
ultrafiltration treated oil, and a 51/4 inch cell is used for
bleaching oil and purified soybean oil.
Chlorophyll: By a standard of the analytical method (JOCS,
1971)
Phospholipid: Lorentz method of the analytical method (JOCS,
1971)
Peroxide Value: By a standard of the analytical method (JOCS,
1971)
Flavor: By an organoleptic test. Standards of evaluation are as
follows.
5.0 Fresh and mild taste, which is satisfactory for food.
4.0 Normal taste for food.
3.0 Unpleasant odor is felt, and taste is not good.
2.0 Somewhat unfittable for food. It is nearly a boundary for
food.
1.0 Bad taste, which is unfittable for food.
Odor by Heating: After heated to 120.degree. C., the odor is
examined by an organoleptic test. Standards of evaluation are as
follows.
A: It is odorless or has an inherent odor and does not have an
unpleasant odor. (good)
B: It has an unpleasant odor but can be used. (common)
C: It has a strong unpleasant odor and is not fittable for
food.
Color by Heating: After allowed to stand in a thermostat at
105.degree. C. for 6 hours, the color is measured by Lovibond
colorimetry (using a 51/4 cell).
Exposure Test: After fluorescent light is applied at 7,000 luxes
for 4 hours, POV and odor by heating are measured.
AOM Test (6 hour value): By a standard of the analytical method
(JOCS, 1971), but by a handy method for measuring a POV after the
passage of 6 hours.
Cold Test: The time at which crystals or white cloudiness are
formed is measured by a standard of the analytical method (JOCS,
1971).
EXAMPLE 2
25 tons of ultrafiltration treated oil were subjected to bleaching
and deodorizing in the same manner as in Example 1 except that acid
treatment was not carried out and activated clay was used in an
amount of 1.2% by weight based on the weight of the ultrafiltration
treated oil, to obtain 20 tons of purified soybean oil.
Properties of the resulting purified soybean oil and those after
preserved by the same manner as in Example 1 are shown in Tables 4
and 5.
EXAMPLE 3
A 25 wt% hexane miscella of a crude rapeseed oil containing 2.29%
by weight (based on the weight of rapeseed oil) of phospholipid,
which was a crude glyceride oil composition, was subjected to
ultrafiltration treatment by circulating and passing through the
above-described membrane module under the same conditions as in
Example 1. From the resulting membrane permeable liquid, hexane was
distilled away to obtain about 30 tons of an ultrafiltration
treated oil.
This treated oil was heated to about 85.degree. C., and a 75%
phosphoric acid solution was added in an amount of 0.05% by weight
based on the weight of the treated oil to carry out acid treatment
by stirring. This ultrafiltration treated oil was then further
heated to 110.degree. C., and activated clay was added in an amount
of 1.2% by weight based on the weight of the treated oil. After
stirred for 30 minutes under 110 mm Hg abs, the activated clay was
filtered out by a filter press to obtain a bleaching oil.
Thereafter, the resulting bleaching oil was heated to 260.degree.
C., and deodorizing was carried out by stripping with sparge steam
in an amount of 4.5% by weight based on the weight of the bleaching
oil under 4 mm Hg abs for 85 minutes to obtain about 25 tons of a
purified rapeseed oil. The resulting purified rapeseed oil was
preserved for 3 months in an outdoor storage tank, and a
preservation test was carried out.
Properties of the crude rapeseed oil used for the membrane
treatment, the ultrafiltration treated oil, the bleaching oil and
the purified oil obtained as described above are shown in Table 6.
For comparison, properties of a purified rapeseed oil which was
obtained by degumming by the conventional chemical process and,
thereafter, carrying out alkali refining, bleaching, dewaxing and
deodorizing are also shown in Table 6.
Further, a preservation test of the purified oil according to the
process of the present invention and the purified oil according to
the conventional chemical process was carried out by the same
manner as in Example 1. The results are shown in Tables 7 and 8,
respectively.
According to the present invention, a rapeseed oil having a
phospholipid content of only 31 ppm was firstly obtained by the
membrane treatment and, thereafter, a purified rapeseed oil which
was superior to that prepared by the conventional chemical refining
process could be obtained by carrying out acid treatment, bleaching
and deodorizing. Further, according to the process of the present
invention, as is clear from the results of a cooling test, dewaxing
was effectively carried out by only the ultrafiltration treatment
as compared with that by the conventional refining process.
EXAMPLE 4
The object of this example was to recover lecithin.
700 l of a phospholipid concentrated liquid (miscella
concentration: 29.2% by weight, and phospholipid concentration:
2.20% by weight), which was a membrane impermeable liquid obtained
in Example 1, was further concentrated by circulating and passing
through the same membrane module as in Example 1 to obtain 75 l of
a concentrated liquid.
Then, 75 l of commercial hexane was added to the concentrated
liquid, and concentration was further continued to obtain 35 l of a
concentrated liquid. 35 l of commercial hexane was added again, and
concentration was carried out to finally obtain 20 l of a
concentrated liquid having a miscella concentration of 31.0% by
weight. From this concentrated liquid, hexane was removed by thin
film vacuum distillation to obtain a high concentration
phospholipid mixture shown in Table 9.
TABLE 1
__________________________________________________________________________
Exposure Test Acid Chloro- Phospho- Peroxide Flavor Odor by Color
by Odor by Analysis Value Color phyll lipid Value Score Heating
Heating POV Heating AOM Cold
__________________________________________________________________________
Test Crude soy- 1.82 Y35-R3.5 -- (2.1) -- -- -- -- -- -- -- -- bean
oil Ultrafiltration 0.95 Y34-R3.4 0.412 25.40 -- -- -- -- -- -- --
-- treated oil Bleached oil 1.05 Y27-R2.6 0.001 23.05 -- -- -- --
-- -- -- -- Purified oil 0.03 Y4-R0.5 0 21.08 0 5.0 A Y10-R1.0 0.28
A 2.10 60 hours or more Comparative 0.03 Y4-R0.4 0 24.38 0 5.0 A
Y9-R0.9 0.64 A' 1.80 25 purified oil
__________________________________________________________________________
*The unit of the phospholipid content is % by weight in only the
case of crude soybean oil, and the others are ppm.
TABLE 2
__________________________________________________________________________
(Purified Oil of the Present Invention) Exposure Test Days Acid
Peroxide Flavor Odor by Color by Odor by Elapsed Value Color Value
Score Heating Heating POV Heating AOM
__________________________________________________________________________
0 0.03 Y4-R0.5 0 5.0 A Y10-R1.0 0.28 A 2.10 15 0.04 Y4-R0.5 0 4.5 A
Y10-R1.0 0.55 A' 2.20 30 0.04 Y5-R0.5 0 4.5 A Y11-R1.2 0.65 A' 2.40
45 0.04 Y5-R0.5 0.05 4.5 A Y12-R1.2 0.70 A' 2.60 60 0.04 Y5-R0.5
0.07 4.0 A Y12-R1.3 0.80 A' 2.80 75 0.04 Y5-R0.6 0.11 3.5 A'
Y15-R1.5 0.80 A' 3.35 90 0.04 Y5-R0.6 0.15 3.5 A' Y16-R1.7 0.90 A'
5.10
__________________________________________________________________________
TABLE 3
__________________________________________________________________________
(Purified Oil of Comparative Example) Exposure Test Days Acid
Peroxide Flavor Odor by Color by Odor by Elapsed Value Color Value
Score Heating Heating POV Heating AOM
__________________________________________________________________________
0 0.03 Y4-R0.4 0 5.0 A Y9-R0.9 0.64 A 1.80 15 0.03 Y4-R0.4 0 4.5 A
Y10-R1.0 0.66 A' 2.20 30 0.04 Y4-R0.4 0 4.5 A Y12-R1.3 0.73 A' 2.80
45 0.04 Y4-R0.4 0.17 4.0 A Y13-R1.3 0.76 A' 3.80 60 0.04 Y4-R0.5
0.27 3.5 A Y14-R1.4 0.85 A' 5.10 75 0.04 Y5-R0.5 0.35 3.5 A'
Y14-R1.4 0.96 A'-B 6.35 90 0.45 Y5-R0.5 0.45 3.5 A' Y14-R1.5 1.00
A'-B 8.50
__________________________________________________________________________
TABLE 4
__________________________________________________________________________
Exposure Test Acid Chloro- Phospho- Peroxide Flavor Odor by Color
by Odor by Analysis Value Color phyll lipid Value Score Heating
Heating POV Heating AOM Cold
__________________________________________________________________________
Test Ultrafiltration 0.95 Y34-R3.4 0.412 25.40 -- -- -- -- -- -- --
-- treated oil Bleached oil 0.98 Y32-R3.3 0.008 20.78 -- -- -- --
-- -- -- -- Purified oil 0.04 Y4-R0.4 0.002 20.02 0 4.5 A Y10-R0.9
0.70 A' 1.80 60
__________________________________________________________________________
TABLE 5
__________________________________________________________________________
Exposure Test Days Acid Peroxide Flavor Odor by Color by Odor by
Elapsed Value Color Value Score Heating Heating POV Heating AOM
__________________________________________________________________________
0 0.04 Y4-R0.4 0 4.5 A Y10-R0.9 0.70 A' 1.80 15 0.04 Y4-R0.5 0 4.5
A Y10-R1.0 0.75 A' 2.10 30 0.05 Y5-R0.5 0.07 4.0 A Y12-R1.2 0.77 A'
2.55 45 0.05 Y5-R0.5 0.20 4.0 A Y13-R1.4 0.85 A' 3.12 60 0.05
Y5-R0.6 0.28 3.5 A' Y14-R1.5 0.89 A'-B 4.93 75 0.05 Y6-R0.6 0.40
3.5 A' Y14-R1.5 0.99 A'-B 5.76 90 0.06 Y6-R0.7 0.48 3.5 A'-B
Y15-R1.5 1.02 A'-B 7.28
__________________________________________________________________________
TABLE 6
__________________________________________________________________________
Exposure Test Acid Chloro- Phospho- Peroxide Flavor Odor by Color
by Odor by Analysis Value Color phyll lipid Value Score Heating
Heating POV Heating AOM Cold
__________________________________________________________________________
Test Crude 2.85 Y58-R5.9- 19.8 (2.29) -- -- -- -- -- -- -- --
rapeseed B3.5 oil Ultra- 1.21 Y47-R5.8- 15.8 31.24 -- -- -- -- --
-- -- -- filtration B2.3 treated oil Bleached 1.32 Y28-R2.9 0.003
28.01 -- -- -- -- -- -- -- -- oil Purified oil 0.03 Y3-R0.4 0 25.59
0 5.0 A Y10-R1.1 0.56 A 2.45 250 Compara- 0.03 Y4-R0.4 0 23.18 0
5.0 A Y9-R1.0 0.70 A' 2.20 150 tive purified oil
__________________________________________________________________________
*The unit of the phospholipid content is % by weight in only the
case of crude rapeseed oil, and the others are ppm.
TABLE 7
__________________________________________________________________________
(Purified Oil of the Present Invention) Exposure Test Days Acid
Peroxide Flavor Odor by Color by Odor by Elapsed Value Color Value
Score Heating Heating POV Heating AOM
__________________________________________________________________________
0 0.03 Y3-R0.4 0 5.0 A Y10-R1.1 0.56 A' 2.45 15 0.03 Y4-R0.4 0 4.5
A Y11-R1.1 0.62 A' 2.61 30 0.04 Y4-R0.4 0.05 4.5 A Y11-R1.1 0.75 A'
2.76 45 0.04 Y4-R0.4 0.08 4.5 A Y12-R1.2 0.89 A' 2.92 60 0.04
Y4-R0.5 0.13 4.0 A' Y12-R1.3 0.96 A' 3.41 75 0.04 Y5-R0.5 0.15 4.0
A' Y13-R1.4 1.05 A'-B 4.26 90 0.04 Y5-R0.6 0.20 3.5 A' R14-R1.4
1.21 A'-B 6.81
__________________________________________________________________________
TABLE 8
__________________________________________________________________________
(Purified Oil of Comparative Example) Exposure Test Days Acid
Peroxide Flavor Odor by Color by Odor by Elapsed Value Color Value
Score Heating Heating POV Heating AOM
__________________________________________________________________________
0 0.03 Y4-R0.4 0 5.0 A Y9-R1.0 0.70 A' 2.20 15 0.03 Y4-R0.4 0 4.5 A
Y10-R1.0 0.74 A' 2.45 30 0.03 Y4-R0.4 0 4.5 A Y11-R1.0 0.83 A' 2.91
45 0.04 Y4-R0.4 0.09 4.0 A' Y11-R1.2 0.90 A' 3.88 60 0.04 Y4-R0.5
0.15 4.0 A' Y12-R1.3 0.98 A'-B 5.77 75 0.04 Y5-R0.5 0.22 3.5 A'
Y14-R1.4 1.10 A'-B 7.24 90 0.04 Y5-R0.5 0.31 3.5 A' Y14-R1.5 1.22
A'-B 9.18
__________________________________________________________________________
TABLE 9 ______________________________________ Composition (%) Food
Additive Invention (e.g., lecithin) Standard
______________________________________ Acetone-soluble 16.3 35.5 40
or less material Acetone-insoluble 81.1 61.2 -- material
Benzene-insoluble 0.21 0.06 0.3 or less material Moisture content
0.29 2.1 2.0 or less Acid value 36.9 23.9 40 or less Color Blackish
-- Light brown yellow or brown
______________________________________
While the invention has been described in detail and with reference
to specific embodiments thereof, it will be apparent to one skilled
in the art that various changes and modifications can be made
therein without departing from the spirit and scope thereof.
* * * * *